In optical communications networks, optical transceiver modules are used to transmit and receive optical signals over optical fibers. On the transmit side of a transceiver module, a light source (e.g., a laser diode) generates amplitude modulated optical signals that represent data, which are received by an optics system of the transceiver module and focused by the optics system into an end of a transmit optical fiber. The signals are then transmitted over the transmit fiber to a receiver node of the network. On the receive side of the transceiver module, the optics system of the transceiver module receives optical signals output from an end of a receive optical fiber and focuses the optical signals onto an optical detector (e.g., a photodiode), which converts the optical energy into electrical energy.
The transmit and receive fiber cables have connectors on their ends, often LC connectors, that are adapted to mate with transmit and receive receptacles, respectively, formed in the transceiver module. A variety of optical transceiver module configurations are used in optical communications network. Some optical transceiver modules have multiple transmit receptacles and multiple receive receptacles for connecting multiple receive and transmit fiber cables to the module. Some transceiver modules having a single receive receptacle and a single transmit receptacle arranged side by side for connecting a single receive fiber cable and a single transmit fiber cable, respectively, to the transceiver module.
The transceiver modules themselves also have mating elements on them that are adapted to mate with mating elements formed on the cages. The cages are contained in racks, and each rack typically includes many cages that are arranged in very close proximity to one another. Each of these cages is configured to receive a transceiver module on the front side of the rack through a front panel of the rack. The transceiver modules are configured so that they may be inserted into and removed from the cages. The modules typically include latching mechanisms that couple to mating features on the cages when the modules are inserted into the cages. In order to remove a module from a cage, the module must be de-latched to decouple the latching mechanism from the features on the cage, which can be challenging when the modules are spaced closely together in the racks.
A variety of different latching mechanism configurations are used on optical transceiver modules. In general, latching mechanisms used on optical transceiver modules include spring loading elements that maintain the latching mechanisms in their locked positions via spring forces. These types of latching mechanisms typically include a bail that is moved to a locked position in order to latch the module to the cage and that is moved to an unlocked position in order to de-latch the module from the cage. When the bail is in the locked position, a latch lock pin extends through an opening formed in the cage to prevent movement of the module relative to the cage and relative to the LC connectors connected to the transmit and receive receptacles. When the bail is in the locked position, the latch lock pin is retracted from the opening formed in the cage, making it possible to remove the module from and insert the module into the cage.
In most optical transceiver module designs, the area around the latching mechanism, and in particular, the opening formed in the module housing with for receiving the latch lock pin, constitute areas that allow electromagnetic interference (EMI) to escape from the transceiver module housing. The Federal Communications Commission provides standards that limit the amount of electromagnetic radiation that may emanate from unintended sources. A variety of techniques and designs are used to shield EMI openings in the transceiver module housings in order to limit the amount of EMI that passes through openings in the transceiver module housing. For example, various metal shielding designs and resins that contain metallic material have been used to cover areas from which EMI may escape from the housings. So far, the known techniques and designs have had only limited success, especially with respect to transceiver modules that transmit and receive data at very high data rates, e.g., 10 gigabits per second (Gbits/sec).
Accordingly, a need exists for an optical transceiver module having an EMI system that is satisfactory at shielding EMI openings in transceiver module housings.